The present invention relates to a focused ion beam apparatus for preparing a sample by irradiating the sample with a focused ion beam from a focused ion beam barrel, and a method of preparing/observing a cross section of a sample.
In the background art, in steps of fabricating a semiconductor device or a thin film magnetic head with a laminated layer structure, a focused ion beam apparatus is utilized as a method of evaluating the fabricating steps. For example, by irradiating a predetermined position of a sample with a focused ion beam from a focused ion beam apparatus to carry out etching, a cross section for observation is fabricated. Further, the cross section for observation is observed by a scanning electron microscope (SEM) (refer, for example, to Japanese Patent No. 2935180 and Japanese patent application publication JP-A-2002-367115). Or, a sample is thinly sliced, also by etching with a focused ion beam. Then, the sliced sample is observed by a transmission electron microscope (TEM). However, according to the method of fabricating the cross section for observation by a focused ion beam, there is a problem that relief lines are formed in the up and down direction in which the focused ion beam is emitted owing to recesses and projections at an irradiated surface of the sample. As a method of fabricating an excellent cross section for observation which resolves such a problem, for example, a method of inclining the sample to be irradiated has been proposed (refer, for example, to Japanese Patent No. 2973211). According to the method, the focused ion beam is skewed with regard to the sample, and therefore, relief lines in the up and down direction are not formed at the sample as described above, and even if there is an unfavorable effect, it would be only slight relief lines in a skewed direction, and an excellent cross section for observation can be fabricated.
However, when the sample is a thin film magnetic head and a cross section for observation is fabricated as in, for example, JP-A-2002-367115, the aspect ratio of the sample is very high, and therefore, there poses a problem that significant relief lines are formed in the direction of the focused ion beam depending on a recessed and projected shape thereof. Although it is confirmed that the method by Japanese Patent No. 2973211 reduces the relief lines, on such a sample having a high aspect ratio, an excellent cross section suitable for observation still cannot be provided, and further, the direction needs to be adjusted for inclining the sample, and therefore, there poses a problem that throughput is reduced.
The invention has been carried out in view of the above-described situation and it is an object of the invention to provide a focused ion beam apparatus capable of improving throughput and a method of fabricating/observing a cross section of a sample capable of providing an accurate observed image.